Hybrid vehicle with in wheel motor and rankine cycle system

ABSTRACT

A hybrid vehicle including one or more in-wheel motors, a power electronics supplying power to the one or more in-wheel motors, and a Rankine cycle system is described. The Rankine cycle system includes a pump driving a working fluid through the Rankine cycle system, a heat exchanger receiving the working fluid from to the pump and connected to the power electronics to cool the power electronics, an evaporator heating the working fluid received from the heat exchanger utilizing heat from an exhaust gas from an engine, an expander receiving the working fluid from the evaporator, and a radiator cooling the working fluid received from the expander.

BACKGROUND

Field of the Disclosure

This disclosure relates generally to improvements to hybrid vehicle.More particularly the present disclosure relates to improving the fuelefficiency of hybrid vehicles (HV) and/or a plug-in hybrid vehicle (PHV)by integrating Rankine Cycle system with other technologies such aspower electronics cooling, turbocharging, and in-wheel motor.

Description of the Related Art

Conventional internal combustion engine (ICE) vehicles are reachingtheir technical limits and will not be able to meet the fuel economyrequirement without additional measures. While, fully electric vehicles(EV) have very high fuel economy and low carbon-dioxide (CO₂) emission;however, their short driving range and long battery charging time limitthe acceptance of the EV. On the other hand, a hybrid electric vehicleis a compromise of traditional ICE vehicle and the EV. A hybrid vehiclecan utilize both ICE and electric energy to enable operation over a longdistance. Additional, different waste energy sources can be utilized tofurther improve the efficiency of the hybrid vehicle. For example usinga Rankine Cycle (RC) system.

The Rankine Cycle is a thermodynamic cycle that converts thermal energyinto mechanical work and is commonly found in thermal power generationplants. The RC system includes four main components: an evaporator; anexpander; a condenser; and a pump connected to form a flow loop of atypical RC system. The pump drives a working fluid to circulate throughthe loop, and the evaporator utilizes a waste heat source to vaporizethe working fluid. The fluid vapor expands in the expander and convertsthermal energy into mechanical power output. Then, the expanded vaporflows through a condenser to convert back into liquid phase, thuscompleting the cycle.

SUMMARY

According to an embodiment of the present disclosure, there is provideda hybrid vehicle. The hybrid vehicle includes one or more in-wheelmotors, a power electronics supplying power to the one or more in-wheelmotors, and a Rankine cycle system. The Rankine cycle system includes apump driving a working fluid through the Rankine cycle system, a heatexchanger receiving the working fluid from to the pump and connected tothe power electronics to cool the power electronics, an evaporatorheating the working fluid received from the heat exchanger utilizingheat from an exhaust gas from an engine, an expander receiving theworking fluid from the evaporator, and a radiator cooling the workingfluid received from the expander.

The hybrid vehicle further includes a preheater located between the heatexchanger and the evaporator. The preheater receives engine coolant toheat the working fluid before passing the working fluid to theevaporator.

The hybrid vehicle further includes a low temperature recuperatorreceiving the working fluid at a first temperature from the heatexchanger and the working fluid at a second temperature from theexpander. The second temperature is greater than the first temperature.

The hybrid vehicle further includes a high temperature recuperatorreceiving the working fluid at a third temperature from the preheaterand the working fluid at a fourth temperature from the expander. Thethird temperature is greater than the fourth temperature.

The hybrid vehicle further includes an exhaust gas recirculation looparound the evaporator partially recirculating the exhaust gas from theoutput of the evaporator to the input of the evaporator.

The forgoing general description of the illustrative implementations andthe following detailed description thereof are merely exemplary aspectsof the teachings of this disclosure, and are not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate one or more embodiments and,together with the description, explain these embodiments. Theaccompanying drawings have not necessarily been drawn to scale. Anyvalues dimensions illustrated in the accompanying graphs and figures arefor illustration purposes only and may or may not represent actual orpreferred values or dimensions. Where applicable, some or all featuresmay not be illustrated to assist in the description of underlyingfeatures. In the drawings:

FIG. 1A illustrates a vehicle with a power split incorporating a firstRankine Cycle system according to an exemplary embodiment of the presentdisclosure.

FIG. 1B illustrates a vehicle incorporating a first Rankine Cycle systemaccording to an exemplary embodiment of the present disclosure.

FIG. 2A illustrates a vehicle with a power split incorporating a secondRankine Cycle system according to an exemplary embodiment of the presentdisclosure.

FIG. 2B illustrates a vehicle incorporating a second Rankine Cyclesystem according to an exemplary embodiment of the present disclosure.

FIG. 3A illustrates a vehicle with a power split incorporating a thirdRankine Cycle system according to an exemplary embodiment of the presentdisclosure.

FIG. 3B illustrates a vehicle incorporating a third Rankine Cycle systemaccording to an exemplary embodiment of the present disclosure.

FIG. 3C illustrates the flow of working fluid between a low temperaturerecuperator, a preheater, and a high temperature recuperator of thethird Rankine Cycle system according to an exemplary embodiment of thepresent disclosure.

FIG. 4A illustrates a vehicle with a power split incorporating a fourthRankine Cycle system according to an exemplary embodiment of the presentdisclosure.

FIG. 4B illustrates a vehicle incorporating a fourth Rankine Cyclesystem according to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

The description set forth below in connection with the appended drawingsis intended as a description of various embodiments of the disclosedsubject matter and is not necessarily intended to represent the onlyembodiment(s). In certain instances, the description includes specificdetails for the purpose of providing an understanding of the disclosedembodiment(s). However, it will be apparent to those skilled in the artthat the disclosed embodiment(s) may be practiced without those specificdetails. In some instances, well-known structures and components may beshown in block diagram form in order to avoid obscuring the concepts ofthe disclosed subject matter.

It is to be understood that terms such as “front,” “rear,” and the likethat may be used herein merely describe points of reference and do notnecessarily limit embodiments of the present disclosure to anyparticular orientation or configuration. Furthermore, terms such as“first,” “second,” “third,” etc., merely identify one of a number ofportions, components, and/or points of reference as disclosed herein,and likewise do not necessarily limit embodiments of the presentdisclosure to any particular configuration or orientation.

Furthermore, the terms “approximately,” “proximate,” “minor,” andsimilar terms generally refer to ranges that include the identifiedvalue within a margin of 20%, 10% or preferably 5% in certainembodiments, and any values therebetween.

Current hybrid vehicles include a transmission system with an electricmotors and an engine to drive the vehicle. The hybrid vehicle canoperate on the electric motor, engine or derive a driving power fromboth the electric motor and the engine, depending on the drivingconditions to achieve a highest efficiency level. Furthermore, whennecessary, the transmission system drives the wheels whilesimultaneously generating electricity using a generator.

However, the hybrid vehicles are limited by the thermal efficiency ofinternal combustion engine (ICE) which is generally below 40%. It hasbeen estimated that the thermal efficiency of a modern internalcombustion (IC) engine is limited to 20-40% while approximately 33% ofthe fuel energy from a typical medium-size passenger vehicle is carriedaway by exhaust gases and approximately 33% is carried away by enginecooling water in an urban traffic conditions.

The waste heat can be harvested by incorporating a Rankine Cycle (RC)system in automobile applications to boost the fuel economy. However, incontrast to typical low-grade waste heat applications such as heatengines in a thermal power plant, automobiles have limited space for theRC system integration. Furthermore, the waste heat is relativelyunstable, for example, in terms of temperature variations. As an add-onsystem to an existing automobile, the RC system integration can leadseveral undesirable component interactions and consequences, asdiscussed below.

Firstly, an increased vehicle weight cannot be avoided due to additionalcomponents of the RC system. The increased weight demands more tractiveeffort to accelerate the vehicle and also imparts more rollingresistance on the tires.

Secondly, a heat exchanger should be added to transfer the heat from theexhaust gas to a working fluid of the RC system. The added pressure dropfrom the heat exchanger causes an increase in an engine back pressurethat affects the engine performance due to loss in engine power.

Thirdly, the heat from the RC condenser should be dissipated to theenvironment, which increases the cooling demand of the automobile. Anextra condenser can occupy extra space for installation and alsoincrease air resistance.

Finally, interaction between the RC system and the vehicle includesutilizing the RC expander power output to drive the wheels. In aconventional hybrid power train, the power of the motor is transferredto the wheels via a long drive shaft, which rotates to transmit thepower to the wheels.

FIGS. 1A, 1B, 2A, 2B, 3A, 3B, 4A, and 4B illustrate four differentconfigurations of the Rankine Cycle (RC) system incorporated in twodifferent types of hybrid vehicles according to the present disclosure.The two different types of hybrid vehicle can be broadly classifiedinto: a vehicle with a power split device; and a vehicle with no powersplit device. Furthermore, the hybrid vehicle can be a front wheeldrive, rear wheel drive, or all-wheel drive. In the present disclosure,the hybrid vehicles are front vehicle drive for discussion purposes onlyand do not limit the scope of the disclosure. It can be appreciated by aperson skilled in art that the present disclosure can be applied toother type of vehicles such as vehicles with a rear wheel drive, andall-wheel drive.

FIG. 1A illustrates a hybrid vehicle 100A having a power split device105 and incorporating a first Rankine Cycle system RC1 according to anexemplary embodiment of the present disclosure. The hybrid vehicle 100Aincludes a vehicle body 10A, two front wheels 110 and 120 fitted within-wheel motors 111 and 121, respectively, two rear wheels 130 and 140,an engine 101 connected to a turbo charger 102, a transmission 103, thepower split device 105, a battery 135, power electronics 132, agenerator 161 and the first Rankine Cycle system RC1 (referred as firstRC system RC1, hereinafter).

The power generated by the engine 101 is transmitted to the front wheels110 and 120 via the transmission 103 and the power split device 105. Thepower split device 105 is a device that splits the power transmitted bythe engine 103 into two components—one to drives the front wheels 110and 120, and second to drive the generator 161. The exhaust gases fromthe engine 101 are carried through an exhaust pipe 171. Optionally, theexhaust gases can be passed through the turbo charger 102, which iscommonly used in turbo-charged automobiles.

The front wheels 110 and 120 can be driven by the rotational input fromthe engine 101, the in-wheel motors 111 and 121, or a combinationthereof. For example, the power from the engine 101 can be transmittedvia the transmission 103 to the front wheels 110 and 120. The power fromthe battery 135 can be transmitted via the power electronics 132 to thein-wheel motors 111 and 121. The in-wheel motor 111 and 121 (alsoreferred as wheel motor, wheel hub drive, hub motor or wheel hub motor)is an electric motor that is incorporated into a hub of a wheel anddrives the wheel directly. The conventional hybrid vehicle includes onemotor that drives a transmission system to supply the rotational inputto the wheels. On the other hand, use of in-wheel motors 111 and 121saves space and enables integration of the first RC system RC1 with thehybrid vehicle 100A. Alternatively, the hybrid vehicle 100A can includetwo or more wheels fitted with two or more motors. For example, threemotors for a three-wheeler, four motors in case of a four-wheeler, fourmotors in case of a six wheeler, etc.

The power electronics 132 is a device that can convert the electricpower from direct current (DC) to alternating current (AC), and canboost the battery voltage to a higher value to drive the in-wheel motors111 and 121. The power electronics 132 includes different electriccomponents such as an inverter, a converter, a transformer, etc.integrated to form a single unit. In operation, the power electronics132 generates a substantial amount of heat, as such requires a coolingsystem.

A typical cooling system has three main components: a cold plate heatexchanger; a radiator; and a pump. The hybrid vehicles are projecting anincreasing demand of higher performance combined with small sized powerelectronics module resulting in an increased heat dissipationrequirement and a better and efficient cooling system that can beaccommodated in the hybrid vehicle with limited space for additionalcomponents.

The first RC system RC1 includes a pump 151, a heat exchanger 153, anevaporator 155, an expander 157, and a radiator 159. The aforementionedcomponents are connected by a RC piping system 152 to form a coolingloop. The RC piping system 152 is a piping system including pipestransporting working fluid (also referred as a refrigerant) throughdifferent components of the first RC system RC1. A refrigerant such asR245fa, H-FE7100, HFC 134a etc. is typically used as the working fluidin a two-phase power electronics cooling loop. Different fluids may beselected depending on the type of power devices and its operationtemperature.

The pump 151 can be a positive displacement type of pump, such as gearpump. However, the other appropriate pumps such as a centrifugal pumpcan be used and does not limit the scope of the present disclosure.

The heat exchanger 153 can be a cold plate heat exchanger. The heatexchanger 153 can be attached to power electronics 132 with thermalinterface material (TIM) therebetween. The cold plate has an inlet andan outlet for the working fluid to circulate through the heat exchanger153. The working fluid flows in and out the cold plate and absorb heatdissipated by the power electronics 132. The heat exchanger 155 can be ashell-and-tube type of heat exchanger. The working fluid (coolant) canflow within the tubes and the hot exhaust gas can flow outside of thetube. The tubes can have fins on the outside surface.

The radiator 159 has conduits through which the working fluid can flowand cool down to a liquid form due to conduction effect. The conduitscan have circular or flat or any other shape of cross-section. Theradiator 159 can have fins on the outside surface. The working fluidflows within the tube and air flows outside of the tube to carry awaythe heat.

The pump 151 is connected to the heat exchanger 153, which is coupledwith the power electronics 132 to extract heat from the powerelectronics 132. The heat exchanger 153 is connected to the evaporator155, which is coupled to the exhaust pipe 171 to extract heat from theexhaust gas passing through the exhaust pipe 171. The evaporator 155 isconnected to the expander 157, which is coupled to the generator 161,for example via a shaft. The expander 157 is connected to the radiator159, which is further connected to the pump 151 to form a closed loop.

The pump 151 pumps the working fluid through the piping system 152extracting heat from different components connected along the pipingsystem 152. The working fluid passes through the heat exchanger 153 thatextracts heat from the power electronics 132 and cools the powerelectronics 132. The evaporator 155 is another heat exchanger thatevaporates the working fluid using the heat from exhaust gas in theexhaust pipe 171. Then, the working fluid (which can be in a superheatedform or a vapor-liquid mixture) flows into the expander 157. As theworking fluid expands in the expander 157, mechanical output isproduced. The output from the expander 157 can be input to the generator161 via a shaft to generate electricity. The electricity generated canbe used to charge the battery 135. The generator 161 can also receivepower from the engine 101 to generate electricity.

The working fluid is further passed through the radiator 159, differentfrom a radiator typically used for cooling engine. The radiator 159 tocool the working fluid and convert it to liquid state before passing theworking fluid to the pump 151.

Optionally, a bypass valve 156 can be included at an input side of theexpander 157. The bypass valve 156 can allow the working fluid to bypassthe expander 157 and direct the working fluid to the radiator 159, whenthe engine is not running.

The pump 151 can be powered be the battery 135. Alternatively or inaddition, the pump 151 can also be powered by the engine 101. Further,the pump 151 can receive input commands such as on and off from acontroller 180. The controller 180 can configured to control the pump151 and/or the bypass valve 156 to control flow of the working fluidthrough the first RC system RC1. The controller can be an electroniccontrol unit (ECU), commonly used in a hybrid vehicle. The functions ofthe controller 180 such as switching a pump on or off, and controllingthe opening and closing of the valve 156 can be implemented in as aseparate circuitry or as sub-module of the ECU.

The controller 180 can receive data from different sensors such as atemperature sensor (not illustrated), a pressure sensor (notillustrated), ignition sensor (not illustrated), etc. One or moretemperature sensor can detect the temperature of working fluid and/orthe temperature of the power electronics 132. The pressure sensor candetect the pressure of the working fluid. The ignition sensor can detectwhether the engine 101 is on or off. Based the on the sensor data, thecontroller 180 can determine the control command. For example, iftemperature of the power electronics 132 increases (or decrease), thecontroller 180 can increase (or decrease) the speed of the pump 151 toincrease (or decrease) the flow rate of the working fluid through thefirst RC system RC1, thus allowing fast (or slow) cooling of the powerelectronics 132. If the ignition is off, the controller 180 can closethe bypass valve 156. Further, the controller 180 can implementoptimization algorithms to optimize the cooling process of the powerelectronics 132.

The first RC system RC1 can be integrated in the hybrid vehicle 100Awith or without the turbo charger 102. The first RC system RC1 operatingin conjunction with a turbocharged engine (e.g., engine 101 connected tothe turbocharger 102) provides advantages over a naturally aspiratedengines (i.e., no turbo charger 102). The evaporator 155 causes apressure drop across the engine 101 that affects the engine performanceand is highly undesirable. Thus, a turbocharged engine can serve twopurposes. First, the turbo charger 102 can utilize the kinetic energy ofthe exhaust gas to compress the air at the intake of the engine 101 forhigher engine performance. Second, the turbocharger can decrease thenegative effect of the increased engine back pressure due to the RCintegration. However, the turbo charger 102 can be omitted from proposedfirst RC system RC1 of the hybrid vehicle 100A, as such does not limitthe scope of the present disclosure.

Alternatively, a hybrid vehicle may not include the power split device105 and still implement the first RC system RC1. FIG. 1B illustrates ahybrid vehicle 100B incorporating the first RC system RC1 according toan exemplary embodiment of the present disclosure. The first RC systemRC1 can output mechanical work to the generator 161 to generateelectricity, there is no need to split part of the power from the engine101 to drive the generator 161.

FIG. 2A illustrates a hybrid vehicle 200A with a power split 105incorporating a second Rankine Cycle system RC2 according to anexemplary embodiment of the present disclosure. The hybrid vehicle 200Ahas a similar construction as the hybrid vehicle 100A, except thathybrid vehicle 200A incorporates the second Rankine Cycle system RC2(referred as second RC system RC2 hereinafter).

The second RC system RC2 includes the pump 151, the heat exchanger 153,a preheater 253, the evaporator 155, the expander 157, and the radiator159. Optionally, a bypass valve 156 can be included. The aforementionedcomponents are connected by a RC piping system 252 to form a coolingloop. The RC piping system 252 is similar to the RC piping system 152,where the RC piping system 252 circulates the working fluid (alsoreferred as a refrigerant) through different components of the second RCsystem RC2 including the preheater 253. The preheater 253 is a heatexchanger that preheats the working fluid before passing through theevaporator 155.

The pump 151 pumps the working fluid through the heat exchanger 153,which cools the power electronics 132. The working fluid is passedthrough the preheater 253, which extracts part of the heat from anengine coolant pipe 272. The engine coolant pipe 272 is a part of theengine cooling system typically incorporated in a vehicle. The preheater253 may evaporate the working fluid by a certain amount (e.g., less than5%-10%) and increase the amount of vapor in the vapor-liquid mixture.The position of the preheater 253 is not restricted to the shownconfiguration. The preheater 253 can be placed after the heat exchanger153 or before the heat exchanger 153. The benefits of the preheater 253also depend on the type of working fluid. For example, if water is used,then the preheater 253 may not provide additional benefits since theboiling point of water is close to the engine coolant temperature (i.e.,approximately 100° C.).

The working fluid is further passed through the evaporator 155, wherethe working fluid is further heated increasing the vapor content of theworking fluid. The working fluid is then passed through the expander157. As the working fluid recovers heat from one more waste heat source,more work can be produced by the expander 157 compared to that producedin the first RC system RC1. The working fluid further passes through theradiator 159, which converts the working fluid in liquid state andpasses to the pump 151.

Furthermore, the controller 180 can be configured to control theoperation of the second RC system RC2 in a similar manner as discussedearlier with respect to the first RC system RC1.

Alternatively, a hybrid vehicle may not include the power split device105 and still implement the second RC system RC2. FIG. 2B illustrates ahybrid vehicle 200B incorporating a second RC system RC2 according to anexemplary embodiment of the present disclosure. The second RC system RC2can output mechanical work to the generator 161 to generate electricity,there is no need to split part of the power from the engine 101 to drivethe generator 161.

FIG. 3A illustrates a hybrid vehicle 300A with a power split 105incorporating a third Rankine Cycle system RC3 according to an exemplaryembodiment of the present disclosure. The hybrid vehicle 300A has asimilar construction as the hybrid vehicle 100A, except that hybridvehicle 300A incorporates the third Rankine Cycle system RC3 (referredas third RC system RC3 hereinafter).

The third RC system RC3 includes the pump 151, the heat exchanger 153, alow temperature recuperator 353 b, a preheater 353 c, a high temperaturerecuperator 353 d, the evaporator 155, the expander 157, and theradiator 159. Optionally, a bypass valve 156 can be included. Theaforementioned components are connected by a RC piping system 352 toform a cooling loop. The RC piping system 352 circulates the workingfluid (also referred as a refrigerant) through different components ofthe third RC system RC3 including the low temperature recuperator 353 b,the preheater 353 c, and the high temperature recuperator 353 d.

The low temperature recuperator 353 b (also referred as LT recuperator353 b) is a heat exchanger located after the heat exchanger 153 andbefore the evaporator 155. The LT recuperator 353 b receives the workingfluid from the heat exchanger 153 and preheats the working fluid beforepassing the working fluid to the evaporator 155. The LT recuperator 353b uses heat from the working fluid exiting from the expander 157 forpreheating purposes.

The preheater 353 c is a heat exchanger that preheats the working fluidoutput from the LT recuperator 353 b and before passing through theevaporator 155. The preheater 353 c uses the heat from the enginecoolant passing through an engine coolant pipe 272.

The high temperature recuperator 353 d (also referred as HT recuperator353 d) is a heat exchanger located after the expander 157 and before theradiator 159. The HT recuperator 353 d receives the working fluid fromthe expander 157, which is used to preheat the working fluid beforepassing the working fluid to the evaporator 155.

Thus, the working fluid exiting from the expander 157 is precooledtwice—first, in the HT recuperator 353 d and then in the LT recuperator353 b. While the working fluid is preheated three times before enteringthe evaporator 155. Such heat exchange reduces the temperaturedifferential within the third RC system RC3.

FIG. 3C illustrates the flow of working fluid and temperaturedifferences between the low temperature recuperator 353 b, the preheater353 c, and the high temperature recuperator 353 d. The LT recuperator353 b receives the working fluid at the input Inb1 at a temperatureTinb1 and at the input Inb2 at a temperature Tinb2. The temperatureTinb2 is greater than Tinb (Tinb2>Tinb1), which causes the working fluidto preheat and exit at the Outb1 at temperature Tinc1. Simultaneously,the working fluid exits at the Outb2 at a temperature Toutb2, which islower than Tinb2. Thus, the working fluid going to the evaporator 155(in FIG. 3A) is preheated, while the working fluid going to the radiator159 (in FIG. 3A) is precooled.

The output from the LT recuperator 353 b is the input to the preheater353 c. As such, the working fluid enters the preheater 353 c at an inputInc1 at a temperature Tinc1. Simultaneously, the preheater 353 c alsoreceives the engine coolant at input Inc2 at a temperature Tinc2. Thetemperature Tinc2 is greater than the temperature Tinc1 (Tinc2>Tinc1),which causes the working fluid to preheat and exit at the Outc1 at atemperature Tind1. Also, the temperature of the engine coolant at Outc2is lowered compared to Tinc2, which can potentially improve the enginecooling efficiency.

The output from the preheater 353 c is the input to the HT recuperator353 d. As such, the working fluid enters the HT recuperator 353 d at aninput Ind1 at a temperature Tind1. Simultaneously, the HT recuperator353 d also receives the working fluid at temperature Tind2. Thetemperature Tind2 is greater than Tind1 (Tind2>Tind1), which causes theworking fluid to preheat and exit at the Outd1 at temperature Tind1.Simultaneously, the working fluid exits at the Outd2 at a temperatureToutd2, which is lower than the temperature Tind2. Thus, the workingfluid going to the evaporator 155 (in FIG. 3A) is preheated, while theworking fluid going to the radiator 159 (in FIG. 3A) is precooled.

The third RC system RC3 follows temperature relationship as below:

-   -   Tinb1<Tinc1<Tind1, also expressed as Toutd1>Toutc1>Toutb1>Tinb1    -   Tinb2>Tinb1; and    -   Tind2>Tind1

Therefore, the third RC system RC3 substantially utilizes the waste heatfrom power electronics 132, the exhaust gas, the engine coolant and theworking fluid from expander 157, and minimizes the temperaturedifferential between the heat source and the working fluid. Thus,providing a high thermal efficiency. However, since additionalcomponents are included for extra heat exchangers, more space issacrificed.

It can be appreciated by a person skilled in art that the presentdisclosure is not limited to the RC3 configuration in FIGS. 3A and 3B.Alternatively, the LT recuperator 353 b and the HT recuperator 353 d maynot be included the same time. Only one of the LT recuperator 353 b andthe HT recuperator 353 d can be included. Furthermore, the order of theheat exchanger 153, the LT recuperator 353 b, the preheater 353 c, andthe HT recuperator 353 d can be changed depending on the selectedrefrigerant and the heat source temperature.

Alternatively, a hybrid vehicle may not include the power split device105 and still implement the third RC system RC3. FIG. 3B illustrates ahybrid vehicle 300B incorporating the third RC system RC3 according toan exemplary embodiment of the present disclosure.

FIGS. 4A and 4B illustrate a hybrid vehicle 400A having a power splitdevice 105 and a hybrid vehicle 400B with no power split device,respectively, incorporating a fourth Rankine Cycle system RC4 (referredas fourth RC system RC4) according to an exemplary embodiment of thepresent disclosure. The fourth RC system RC4 includes an exhaust gasrecirculation (EGR) loop formed around the evaporator 155. The EGR looprecirculates the exhaust gas in the exhaust gas pipe 171. The EGR loopincludes a first bypass valve 450 at the input side of the evaporator155, a second bypass valve 454 at the output side of the evaporator 155,a pipe 455 connecting the second bypass valve and the exhaust gas pipe171.

The exhaust gas from the engine 101 is passed through the first bypassvalve 450 to evaporator 155. The exhaust gas exiting the evaporator 155is then redirected by the second bypass valve 454 to the input side ofthe evaporator 155. Thus, the exhaust gas flowing out of the evaporator155 at a low temperature is partially recirculated and mixed with ahigh-temperature exhaust gas from engine 101. As such, both the flowrate and the exhaust gas temperature at the evaporator 155 inlet can beactively controlled according to the driving profile to provide optimaloperating conditions for the fourth RC system RC4. The EGR loop can alsobe added to the first, second and the third RC systems RC1, RC2, andRC3.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the present disclosures. Indeed, the novel methods, apparatusesand systems described herein can be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods, apparatuses and systems described herein can bemade without departing from the spirit of the present disclosures. Theaccompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thepresent disclosures.

What is claimed is:
 1. A hybrid vehicle comprising: one or more in-wheelmotors; a power electronics supplying power to the one or more in-wheelmotors; and a Rankine cycle system comprising a pump driving a workingfluid through the Rankine cycle system, a heat exchanger receiving theworking fluid from the pump and connected to the power electronics tocool the power electronics, an evaporator heating the working fluidreceived from the heat exchanger utilizing heat from an exhaust gas froman engine, an expander receiving the working fluid from the evaporator,and a radiator cooling the working fluid received from the expander. 2.The hybrid vehicle according to claim 1, further comprising a preheaterlocated between the heat exchanger and the evaporator.
 3. The hybridvehicle according to claim 2, wherein the preheater receives enginecoolant to heat the working fluid before passing the working fluid tothe evaporator.
 4. The hybrid vehicle according to claim 2, furthercomprising a low temperature recuperator receiving the working fluid ata first temperature from the heat exchanger and the working fluid at asecond temperature from the expander.
 5. The hybrid vehicle according toclaim 4, wherein the second temperature is greater than the firsttemperature.
 6. The hybrid vehicle according to claim 2, furthercomprising a high temperature recuperator receiving the working fluid ata third temperature from the preheater and the working fluid at a fourthtemperature from the expander.
 7. The hybrid vehicle according to claim6, wherein the third temperature is greater than the fourth temperature.8. The hybrid vehicle according to claim 1, further comprising anexhaust gas recirculation loop around the evaporator partiallyrecirculating the exhaust gas from the output of the evaporator to theinput of the evaporator.
 9. A Rankine cycle system comprising: a pumpdriving a working fluid through the Rankine cycle system; a heatexchanger receiving the working fluid from the pump and connected topower electronics of a hybrid vehicle to cool the power electronics; anevaporator heating the working fluid received from the heat exchangerutilizing heat from an exhaust gas from an engine of a hybrid vehicle; apreheater located between the heat exchanger and the evaporator; anexpander receiving the working fluid from the evaporator; and a radiatorcooling the working fluid received from the expander.
 10. The Rankinecycle system according to claim 9, wherein the preheater receives enginecoolant to heat the working fluid before passing the working fluid tothe evaporator.
 11. The Rankine cycle system according to claim 9,further comprising a low temperature recuperator receiving the workingfluid at a first temperature from the heat exchanger and the workingfluid at a second temperature from the expander.
 12. The Rankine cyclesystem according to claim 11, wherein the second temperature is greaterthan the first temperature.
 13. The Rankine cycle system according toclaim 9, further comprising a high temperature recuperator receiving theworking fluid at a third temperature from the preheater and the workingfluid at a fourth temperature from the expander.
 14. The Rankine cyclesystem according to claim 13, wherein the third temperature is greaterthan the fourth temperature.
 15. The Rankine cycle system according toclaim 9, further comprising an exhaust gas recirculation loop around theevaporator partially recirculating the exhaust gas from the output ofthe evaporator to the input of the evaporator.